# Important Definitions Regarding Parabola

**Focus**

The fixed point used to draw the parabola is called the focus (F). The focus is F(a, 0).

**Directrix **

The fixed line used to draw a parabola is called the directrix of the parabola. The equation of the directrix is x = −a.

**Axis**

The axis of the parabola is the axis of symmetry. The curve y^{2} = 4ax is symmetrical about x-axis and hence x-axis or y = 0 is the axis of the parabola.

The axis of the parabola passes through the focus and perpendicular to the directrix.

**Vertex**

The point of intersection of the parabola and its axis is called its vertex. The vertex is V(0, 0).

**Focal Distance**

The focal distance is the distance between a point on the parabola and its focus.

**Focal Chord**

A chord which passes through the focus of the parabola is called the focal chord of the parabola.

**Latus Rectum**

It is a focal chord perpendicular to the axis of the parabola. The equation of the latus rectum is x = a.

**End points of latus rectum and length of latus rectum**

To find the end points, solve the equation of latus rectum x = a and y^{2} = 4ax.

y = ±2a

The length of latus rectum = 4a